(EE NOMENGE ATURE Ohhh AKG SURE IROR 
FORMATIONS. 
“THE Iron Ore Deposits of the Lake Superior Region,” by 
Professor C. R. Van Hise, recently published in the 7wwenty-first 
Annual Report of the United States Geological Survey, is a most 
noteworthy contribution to Lake Superior geology. While 
especially valuable to mining men, for whom it was prepared, 
its references to stratigraphy are most interesting to geologists. 
In a footnote (p. 317) it is stated that the evidence upon which 
the geological succession is based will be fully given in a 
monograph upon the Vermilion District to be published later. 
While for the most part in accord with the author’s stratigraphy, 
I do not agree with his nomenclature, and this paper is written 
with the hope that by discussion unanimity may be reached in 
this matter also. Owing to its importance, I here quote almost 
in full the footnote referred to above: 
The foregoing papers render it unnecessary for me here to take up the 
general stratigraphy of the Lake Superior region. However, our work north 
of Lake Superior, in northeastern Minnesota and Canada, has upon two 
points modified our published conclusions as to succession and correlation. 
Those who compare this paper with earlier papers will note two important 
modifications. First, the Archean has heretofore been supposed to be com- 
posed wholly of igneous rocks; no sediments have been recognized in this 
division of the pre-Cambrian. The north-shore work, however makes it very 
probable that certain of the sedimentary iron-bearing formations must be 
included in the Archean. As examples of such are the productive iron 
formations of the Vermilion and Michipicoten districts. This modification 
is important from a theoretical point of view, since it will make changes 
necessary in my general definition of the Archean and of the Algonkian. 
The Algonkian has been defined to include all pre-Cambrian sedimentary 
rocks. The Archean has been defined to include all pre-Algonkian rocks, 
and has been supposed to contain igneous rocks only. These definitions 
must be modified so as to include in the Algonkian all pre-Cambrian series 
which are dominantly of sedimentary origin, or equivalent in age with those 
which are dominantly of sedimentary origin. The Archean must be defined 
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